1. Field of the Invention
The present invention relates to a production process for a surface-mounting ceramic light emitting diode (LED) package, a surface-mounting ceramic LED package produced by the production process, and a mold for producing the package.
2. Technical Background
LEDs are widely applied as backlighting for displays and light sources for general illumination and the like. LED packages can be broadly classified into dome packages and surface-mounting packages. In the case of the dome LED packages, an LED chip is mounted to a lead frame and the periphery thereof is molded into the shape of a dome with resin. The reason for molding the resin into the shape of a dome is to focus the light from the chip forward by refraction, thereby improving the amount of radiated light. In the case of the surface-mounting packages, an LED chip is placed in the bottom of a recess in a concave board and sealed with resin. Since surface-mounting types allow lower mounting height, smaller size and lighter weight, they have a wide range of applications and have a promising future. In the case of surface-mounting types, instead of refracting light with a molded resin in the manner of dome types, the walls of concave portions are facing upward (in the direction of the openings of the concave portions) and inclined so as to spread out, thereby serving to enhance the amount of radiated light.
Since LED chips are able to radiate light of a plurality of colors, LED devices can be obtained that radiate various colors of light by combining LED chips. However, when a plurality of LED chips is placed inside the same concave portion, there was the problem of light radiated from a certain LED chip being interfered with by the light from an adjacent LED chip. For example, in the case of obtaining white light, a method is employed that combines red (R), green (G) and blue (B) light. Ordinary LED chips are in the form of flat squares, and the light radiating therefrom lacks directivity and is emitted from nearly the entire surface thereof. Since light radiated from the sides of a chip opposes light radiated from an adjacent chip, radiated light of different wavelengths interfere causing the light to be mutually diminished. This results in problems of attenuation of the amount of radiated light and the occurrence of unevenness in the amount of light. In order to overcome this interference of light, a partition is provided in the bottom of the concave portions of surface-mounted LED devices in an attempt to reduce optical interference occurring between LED chips.
According to WO 2002/017401, the problem of a reduction in the amount of light radiated from the entire LED device is overcome by providing partitions between a plurality of LED chips in the bottom of concave portions of a plastic LED device to prevent light radiated from one LED chip from being interfered with by the light from another LED chip.
However, plastic is used for the package substrate in WO 2002/017401. Since plastic may be deteriorated by ultraviolet rays contained in light emitted from LED chips, it is not optimal for use in LED packages. In addition, although high-output LED chips emit radiated light of high brightness, the amount of heat dissipated also increases. Since plastic packages lack heat resistance, thermal deterioration is considerable thereby resulting in the problem of a short service life of the package itself.
On the other hand, although ceramic packages have superior heat resistance, they had the problem of being inferior to the moldability of plastic products with respect to fine structures such as inclined or curved radiated light reflecting surfaces or partitions between chips. For this reason, ceramic packages have difficulty in guiding light radiated from an LED chip in a desired direction, ultimately resulting in a loss in the amount of radiated light. Therefore, the shortcoming of ceramic packages having inferior moldability with respect to fine structures was overcome by effectively utilizing the properties of thermoplastic green sheets.
The present invention overcomes many of these problems by providing a production process for making a ceramic LED package, enabling partitions to be formed both easily and reliably, making a ceramic LED package having partitions, and making a mold for molding a ceramic LED package.